Embodiments of the present invention relate in general to an out-of-order (OoO) processor and more specifically to a scalable dependency matrix with multiple summary bits in an issue queue of an OoO processor.
In an OoO processor, an instruction sequencing unit (ISU) dispatches instructions to various issue queues, renames registers in support of OoO execution, issues instructions from the various issue queues to the execution pipelines, completes executed instructions, and handles exception conditions. Register renaming is typically performed by mapper logic in the ISU before the instructions are placed in their respective issue queues.
The ISU includes one or more issue queues that contain dependency matrices for tracking dependencies between instructions. A dependency matrix typically includes one row and one column for each instruction in the issue queue. As the number of instructions in the issue queues continues to increase, the amount of space and power taken up by each of the dependency matrices is growing.